Development of nanotechnology is now rapidly providing us with new types of materials in our everyday lives. They have applications in health care products, cosmetics, paints, cleaning products, catalysts, antibacterial coatings, self cleaning surfaces, pesticides, nutritional supplements and food packaging. These open up many new technical opportunities and we can see large added values and benefits with the new applications, but there are also potential risks for health and the environment. Do we dare open Pandora’s box, or is it safest to keep it closed? How well can these new nanomaterials be dealt with by the existing chemical legislation?
As recently as last year, after many years of preparations and negotiations, the new chemical legislation REACH came into force in the EU. REACH will cover general industrial chemicals that are produced in, or imported into, the EU. It has been determined by the EU Commission that nanoparticles shall come under the definition of a substance in accordance with REACH. The message of the Commission is that all elements of REACH (registration, information management, risk reduction, authorisation etc) shall also apply to nanomaterials. Let us therefore briefly discuss how nanomaterials can be dealt with in REACH and what adjustments may be required.
Small quantities, large numbers
In the first place, the requirements of the legislation, to deliver information on the substance and its risks, are governed by production volume (annual tonnes/producer or importer), and many nanomaterials are as yet made in relatively small quantities. However, even very small quantities (by weight) can contain a very large number of nanoparticles. Concentration (such as number of particles/volume) increases rapidly, as does the specific surface area, as the diameter decreases. As an example, ten-nanometre particles have a surface area of several hundred square metres per gram. Nanomaterials with a considerable number of particles and large reactive surfaces can thus be produced without activating the tonnage triggers which decide whether information has to be reported to REACH.
Description is chemical rather than physical
In order that the environmental or health risks of a substance may be assessed, it must be possible for it to be defined clearly and unequivocally. In REACH, such descriptions mainly have a chemical rather than a physical basis. Since there are as yet no adequate and scientifically agreed terms for describing a number of properties at nano level, neither are these terms included in REACH’s glossary. There is therefore a risk that various nanomaterials and their macroscopic equivalents with the same chemical (stoichiometric) composition cannot be described correctly but may be considered to be one and the same substance. This is despite the fact that these differ by a nanoscale and may have drastically different characters, reactivity and potentially different behaviours in the environment, and may give rise to different biological effects. In the nano region, technical development is proceeding so rapidly at present that different phenomena are utilised in products before it has been decided how the underlying molecular, particulate and surface structures are to be described.
Not relevant for nanomaterials
The accepted practice is that the behaviour of chemicals in the environment is attempted to be described with reference to chemical equilibrium concepts, for example to predict how a chemical is distributed between air and water or between water and aquatic organisms. A similar set of chemical descriptors, for example molecular weight, vapour pressure and water solubility, are therefore needed as the basis for the assessment of the distribution in the environment which must be done in accordance with instructions in REACH.
These conventional criteria are relatively irrelevant for nanomaterials, and a new set of relevant descriptors such as size distribution, surface area, surface charge and crystal structure must therefore be produced and implemented. This work has begun in both academic research and international standardisation organisations such as OECD and ISO where various players are represented. It has also been found that surface functionalisation of nanoparticles is yet another parameter which is a very important descriptor for both behaviour in the environment and for uptake by organisms.
Another example from our research has shown that the surface charge dynamics of the particles largely govern behaviour in the agglomeration of e.g. titanium dioxide-nanoparticles. This illustrates the importance of surface charge which is a relevant criterion for the prediction of the distribution processes of nanoparticles in the environment. This will, in turn, affect the degree of exposure of humans and other organisms. In addition, both experiments and modelling have shown that surface charge properties are, in turn, affected by particle size, and this further demonstrates the importance of an adequate physico-chemical characterisation of nanoparticles.
A similar picture appears in evaluating the uptake of nanoparticles. In view of the different surfaces (and thus different reactivities) of nanoparticles, their different sizes and shapes, it is evidently insufficient to place reliance on only a mass concentration to describe the “concentration” of nanoparticles in a human target organ or in a certain scenario for environmental exposure. There is therefore a crying need of further development and evaluations of improved dosimetric measures such as number per concentration, surface area or even more vaguely defined concepts such as “bioavailable surface area”.
Nano-adapted criteria are required
Only one set of descriptors, which are suited for nanoparticles, can form a proper basis for subsequent descriptions of toxicity and eco-toxicity for nanomaterials, for example in the form of dose-response relationships or (eco)toxicological limit values.
In the present situation, there is thus a lack of fundamental knowledge concerning uptake, distribution, elimination and pharmaco-dynamic interactions for nanoparticles in a number of potentially exposed organisms. This is largely due to the absence of adequate terminology and developed scientific knowledge. This limits the development of adequate test procedures, including the choice of test species, indices of biological effects, and appropriate exposure regimes. We are a long way from tests which, on the one hand, protect human health and the environment and, on the other, make an optimised use of available resources and minimise the need for animal experiments.
To sum up, REACH and its instructions for making risk assessments do not give sufficient consideration to the specific properties which substances at nanoscale exhibit. It will thus be problematic to evaluate possible health and environmental risks by only the conventional chemocentric procedures. The EU Parliament recently applied the prudence concept to some of these aspects by supporting, with a large majority, a resolution from the Swedish MEP Carl Schlyter which, in reality, asks for a moratorium on nanotechnology pending the development of an adequate risk assessment methodology. (See link No 1 at the end of this article). So far, the Commission has not replied to this report but they have called for a general consultation on the risk assessment of nanotechnology that is open to all European organisations and citizens up to 19 June 2009. (See link No 2 at the end of the article).
The next logical step in this evaluation will be to examine other parts of the legislation for chemical and risk assessment which correspond to more specific products or fields of application. A review must then be made to see whether these are applicable to nanomaterials, for example with regard to labelling requirements and controls.
Author
:
Martin Hassellöv
is researcher at the Department of Chemistry, Göteborg University
Thomas Backhaus
is resercher at Department of Plant and Environmental Science, Göteborg University
Sverker Molander
is researcher at Environmental Systems Analysis, Energy & Environment, Chalmers University of Technology